The present invention relates to gas-type circuit breakers, and more specifically to an improved arrangement for operating a gas blast valve used in circuit breakers of the two-pressure type.
As transmission line voltages have attained ever higher values, the need has increased for circuit breakers of commensurately increased capacity. While in the past circuit breakers operating in air, or using vacuum contactors, have been adequate recent designs have incorporated interrupters operating in an environment of sulfur hexafluoride, or SF.sub.6. In order to extinguish the arc which is typically drawn between separating contacts at extremely high voltages, means are provided to direct a high-pressure jet of SF.sub.6 gas between the contacts in order to literally "blow out" the arc.
Such circuit interrupters typically are of two varieties. In one, termed a "puffer" breaker, mechanical pistons or bellows are provided to compress gas which is disposed in the interrupting chamber, causing it to flow in the desired fashion. In the other, or "two-pressure", approach the gas is compressed into a reservoir and maintained at a high pressure by a valve. Operation of the circuit breaker by means of a linkage causes the valve to be opened momentarily, whereupon the previously-pressurized gas rushes out through a passageway and is directed to the area between the separating interrupter contacts.
The timing and sequencing of the valve operation in the two-pressure type of circuit breaker is critical. Moreover, since such breakers are typically used in threes, due to their application in three-phase power systems, the elastic characteristics of the linkages and the connecting links used to synchronize them make it extremely difficult to properly time the operation of the blast valve. In addition, due to the extreme speed involved and the necessarily robust nature of the linkages, the mechanical forces which are generated are extremely high. Previously-known linkages for operating blast valve have often been difficult to adjust and to synchronize. Further, the type of valve used typically requires a short, reciprocating stroke which is accurately timed, which is difficult to accomplish with the required precision and accuracy.
It is therefore an object of the present invention to provide an improved valving mechanism for a two-pressure circuit breaker.
Another object of the present invention is to provide a linkage which will "crack" a valve by a fixed amount regardless of the length of travel of the operating mechanism.
It is yet another object of the invention to provide a fully adjustable valve actuating means for a two-pressure circuit breaker whose operation is adjustable independently of the main operating linkage of the breaker.